A disgruntled employee at Tesla has caused “extensive and damaging sabotage,” according to the company’s CEO Elon Musk.

In an email sent to employees late Sunday night, Musk revealed an employee had broken into the company’s computer systems in an effort to disrupt operations.

The message, as first reported by CNBC, stated the employee made direct code changes to the Tesla Manufacturing Operating System using false usernames. The unnamed employee also exported “large amounts of highly sensitive Tesla data” to unknown third parties.

“His motivation is that he wanted a promotion that he did not receive,” wrote Musk. “In light of these actions, not promoting him was definitely the right move,” he said.

Musk added that an in-depth investigation would continue this week, asking employees to remain “extremely vigilant.”

Tim Erlin, VP of Product Management and Strategy at Tripwire, noted that while insider threats have decreased in visibility as we’ve seen more sophisticated nation-state and cybercrime attacks, such incidents still have the ability to cause significant damage.

“Telsa will have to investigate all the changes made by this rogue employee, including those made under falsified username and credentials. Without detailed change detection, that’s an incredibly tedious task,” Erlin said.

“Sometimes even authorized changes can be suspicious and require investigation. Organizations are used to looking for unauthorized changes as a means of detecting malicious activity, but a skilled insider isn’t as likely to get caught in the same way.” Added Erlin.

The incident comes as the Palo Alto-based company ramps up the production of its Model 3, aiming to produce 5,000 or more vehicles per week by the end of June.

In a separate email sent Monday morning, employees were informed of a small fire that briefly halted production but was quickly contained, reported CNBC.

“Could just be a random event, but as Andy Grove said, ‘Only the paranoid survive,’” said Musk. “Please be on the alert for anything that’s not in the best interests of our company.”